Condition responsive apparatus which provide an indication or control an operation in response thereto, are well-known in the prior art. Such devices have been used in many diverse types of environments. For example, it is often desirable to determine the pressure of a fluid in a system or vessel, and condition responsive apparatus have been provided for this purpose. Such an apparatus typically includes a pressure sensitive element such as a Bourdon tube which, when connected to a source of external pressure, deflects by an amount proportional to this pressure. This deflection can then be transduced into a mechancial or electrical output to provide an indication of the fluid pressure in the tube or, alternatively, to control some other operation. An apparatus of this type is shown in U.S. Pat. No. 4,184,377 to Hubbard which discloses a hydraulic pressure transducer for use in conjunction with a vehicle braking system.
Although such condition responsive apparatus have proved generally effective for indicating a condition or controlling an operation in response to a change in the condition, these devices often utilize complex electronic control systems to provide the required output. Such control systems increase the cost of the apparatus and reduce its reliability. There is therefore a need for an improved condition responsive apparatus which is cost effective to manufacture, but which provides superior performance and reliability.